| P wave
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- left atrial enlargement: negative portion of the P wave in lead V1 ≥ 0.1 mV in depth and ≥ 0.04 s in duration
- right atrial enlargement: peaked P wave in leads II and III or V1 ≥ 0.25 mV in amplitude
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| QRS complex
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- frontal plane axis deviation: right ≥ +120° or left –30° to –90°;
- increased voltage: amplitude of R or S wave in in a standard lead ≥2 mV, S wave in lead V1 or V2 ≥ 3 mV, or R wave in lead V5 or V6 ≥ 3 mV;
- abnormal Q waves ≥ 0.04 s in duration or ≥ 25% of the height of the ensuing R wave or QS pattern in
two or more leads;
- right or left bundle branch block with QRS duration ≥ 0.12 s;
- R or R' wave in lead V1 ≥ 0.5 mV in amplitude and R/S ratio ≥ 1.
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| ST-segment, T-waves, and QT interval
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- ST-segment depression or T-wave flattening or inversion in two or more leads;
- prolongation of heart rate corrected QT interval (QTc) > 0.44 s in males and > 0.46 s in females.
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| Rhythm and conduction abnormalities
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- premature ventricular beats or more severe ventricular arrhythmias;
- supraventricular tachycardias, atrial flutter, or atrial fibrillation;
- short PR interval (< 0.12 s) with or without ‘delta’ wave;
- sinus bradycardia with resting heart rate ≤ 40 beats/mina;a
- first (PR ≥ 0.21 sb), second or third degree atrioventricular block.
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| aIncreasing less than 100 beats/min during limited exercise test.
bNot shortening with hyperventilation or limited exercise test.
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